If you're thinking of buying a residential property and you're about to load up with debt, look out.

The Reserve Bank looks set to introduce new debt-to-income lending ratios to try to take some heat out of the market.

Kiwibank economists today said that heat was "becoming unbearable" after new national house sale data emerged and the Reserve Bank was about to take a larger hose to it.

That move will undoubtedly be limiting amounts loaned by major trading banks to the riskier clients who are trying to load up with high debt levels to buy properties whose values they believe will continue only to rise.

The Reserve Bank doesn't see it that way and has expressed concern.

The latest Real Estate Institute figures out this morning showed median prices rose 25.2 per cent annually, from $659,500 to a record $826,000 and Auckland house prices also set a record, up 28 per cent from $918,000 last July to $1,175,000 last month.

Kiwibank economists Jarrod Kerr, Jeremy Couchman and Mary Jo Vergara reacted, saying there was now no doubt what was about to happen.

"The heat from the housing market is getting a little too hot to handle. The market just hasn't responded quick enough to recent policy changes targeting property investors. High-risk debt continues to build so financial stability concerns have pushed the Reserve Bank to act," the economists said.

The Reserve Bank also now has a directive from the Minister of Finance, Grant Robertson, "…to have regard to house price sustainability when making financial stability decisions".

The economists said that was a green light to use more debt-to-income lending restrictions, "meaning the RBNZ has a larger firehose to douse the market with".

A little of the blaze damped down in today's numbers but even that could have been somewhat artificial: New Zealand house sale volumes fell by 12 per cent last month compared to July last year and some regions also saw big declines. Nelson house sale volumes halved in the year to July 2021 and Hawke's Bay sales fell by 28 per cent.

Last July, 8135 properties were sold throughout New Zealand but only 7187 were sold last month.

But Jen Baird, REINZ chief executive, said last July was unusual because New Zealand had just come out of its high alert level lockdowns then. That had boosted last year's sales.

"House prices have continued to rise across the country as every region saw a year-on-year increase from July 2020.

"The last two months have shown early indications that the rate of growth is starting to ease, however, it is too early to say whether this is the usual winter easing we would normally see or if the Government's intervention in the market and signalled changes to the OCR are starting to take effect.

The strength of the market has again been reflected in the REINZ House Price Index which reached a new high on the index nationally.

Every region reached a record level last month, Baird said.

In Auckland, six out of seven districts had new record median prices: North Shore City $1,375,000, Rodney District $1,240,000, Waitakere City $1,100,000, Manukau City $1,075,000, Papakura District $913,000 and Franklin District $885,000.